This application claims priority from Israeli Patent Application No. 126165, entitled xe2x80x9cApparatus For The Orthoganol Movement of a CCD Sensorxe2x80x9d filed on Sep. 10, 1998, incorporated herein by reference.
The present invention relates to digital cameras in general and in particular to the movement of CCD sensors within digital cameras.
One of the main problems associated with digital cameras is obtaining a sufficiently high resolution. This problem is amplified with color cameras, having color CCD sensors, such as the Leaf Catchlight digital camera, manufactured by Scitex Corp., Herzlia, Israel. The benefit of using a color CCD, is the option of taking one-shot pictures, such that a moving object might be photographed too.
FIG. 1 schematically illustrates the pixel arrangement of a color CCD sensor. In the color CCD sensor, one third of the pixels are green (referenced G), one third are blue (referenced B) and one third are red (referenced R), thus the total resolution is one third.
Various methods for increasing the resolution have been developed over the past few years. One method is based on a filter-wheel, which is placed in front of the CCD sensor and requires three shots for each picture; one shot for each base-color. An example of such a device is the Leaf DCB-2 digital camera, manufactured by Scitex Corp., Herzlia, Israel.
Another method consists of three CCDs with dichroitic mirrors in front. All three CCDs view the same picture, thus increasing the resolution by factor of three. An example of such a device is the Smart Scanner head, manufactured by Scitex Corp., Herzlia, Israel.
A third method is based on a color CCD sensor, as described in FIG. 1, which is placed on an X-Y piezoelectric driven stage. Reference is now made to FIG. 2, which schematically illustrates the use of an X-Y stage. Generally, a pixel, for example pixel xe2x80x9cAxe2x80x9d, of an object 1, when viewed via the camera lens 2, is inverted by the lens 2 and is sensed by CCD sensor 3 in the position 7 indicated by B (blue) sensing pixel of sensor 3. The X-Y stage of the piezoelectric driver is schematically shown by elements 4 and 5 respectively. When the piezoelectric driver 5, for example, moves the sensor one pixel in the Y direction, pixel xe2x80x9cAxe2x80x9d will xe2x80x98fallxe2x80x99 on pixel G (green) of the sensor 3, indicated 8, instead of pixel B (blue). Thus, the color of pixel xe2x80x9cAxe2x80x9d is sensed by a sensor pixel having another color (say green). Similarly, when driver 4 moves the sensor in the X direction, the viewed pixel xe2x80x9cAxe2x80x9dxe2x80x98fallsxe2x80x99 on a pixel of another color R (red) indicated 9. Thus, by taking three shots of each pixel, each pixel is photographed in its three basic colors (R, G and B). An example of such a device is the Carnival digital camera, manufactured by Scanview of Denmark.
EP Patent 0396687 to Lenz, describes the use of separate piezo-actuators for shifting an image in the X and Y directions between individual frame pickups, relative to a CCD junction detector, so that at least three color separations are positioned in succession at the same picture position.
Unfortunately, all the above methods are either expensive and/or complicated to manufacture.
Present day still cameras utilize a fixed CCD sensor. For example, the Ftf 3020 color camera, manufactured by Philips of the Netherlands, which uses a rectangular CCD having 2000 pixels in heightxc3x973000 pixels in width. Cameras having such rectangular CCD have a major disadvantage when photographing a vertical picture. Since the orientation of the picture and the sensor are perpendicular to each other, there is loss of information. This is illustrated in FIG. 3, to which reference is now made.
A horizontal object 1 viewed by a camera lens 2, xe2x80x98fallsxe2x80x99 completely on the CCD sensor 3. However, when a vertical object, referenced 10, is viewed, only part of the object 10 xe2x80x98fallsxe2x80x99 on the CCD sensor 3, while other parts of the object, indicated by dashed lines 12, are xe2x80x98lostxe2x80x99.
To overcome this problem, the camera is usually rotated 90, by rotating the base (seating the camera on a conventional tripod, for example). However, rotating the camera base causes misalignment of the camera vis-a-vis the picture being viewed. Usually, the misalignment is corrected by re-adjusting the stand. This procedure is time-consuming and inconvenient.
The present invention provides apparatus for moving a CCD sensor in the X-Y direction, which overcomes the limitations and disadvantages of the prior art.
The present invention further provides orthogonal X-Y movement apparatus, which allows high-resolution color photography in both the X and Y directions, by micro-movement of the CCD sensor.
The present invention further uses a specific arrangement of the three colors on the CCD sensor, thus providing, in conjunction with the suggested micro-movement of the CCD sensor, a sampling sequence that is optimal for use in a digital camera that may alternately serve as one-shot or three-shot camera.
The present invention in addition provides a rotatable mount for rotating a CCD sensor within a pre-determined degree of limitation from a first position to a second position, such as 90 degrees from portrait mode to landscape mode, without needing to rotate the camera base and consequent misalignment of the camera. The rotatable mount can be used together with the orthogonal X-Y apparatus.
There is thus provided, in accordance with a preferred embodiment of the present invention, apparatus for the orthogonal (X,Y) movement of a CCD sensor within a digital camera body which includes a CCD plate to which the CCD sensor is connected, a linear actuator for providing movement in orthogonal X,Y directions to the CCD plate, the linear actuator having a first axis disposed at 45 degrees to the X and Y directions, and means for transferring movement between the linear actuator and the CCD plate.
Furthermore, in accordance with the preferred embodiment of the resent invention, the apparatus further includes a base plate connected to the camera body and wire springs connecting the base plate to the CCD plate.
Furthermore, in accordance with a preferred embodiment of the present invention, the means for transferring movement includes a movable member attached to the linear actuator, the actuation of the linear actuator causing the movable member to move either backwards or forwards along the first axis.
In addition, in accordance with a preferred embodiment of the present invention, the means for transferring movement further includes first and second rotatable eccentric arms supported by corresponding first and second support rods, respectively, the first and second rotatable eccentric arms being in contact with the CCD plate; and first and second rods, each of the first and second rods having a proximate and a distal end, wherein the distal end of each of the first and second rods is attached to the first and second eccentric arms, respectively, wherein the proximal end of each of the first and second rods is in contact with the movable member, and wherein the proximal end of each of the first and second rods is slidably retained by the base plate.
The transferring movement means also includes rotatable annuluses fitted to the first and second eccentric arms; and rotating bearings attached to the CCD plate, the rotating bearings in contiguous contact with the rotatable annuluses to reduce friction between the first and second eccentric arms and the CCD plate.
Furthermore, in accordance with a preferred embodiment of the present invention, the first and second rods are in contiguous contact with opposite ends of the movable member; the first rod being positioned behind the movable member proximate to one end of the movable member, and the second rod being positioned in front of the movable member proximate to the other end of the movable member.
Furthermore, in accordance with a preferred embodiment of the present invention, the apparatus further includes first and second restraining plates; each of the first and second restraining plates being attached at a first end to the base plate, and first and second springs attached to the CCD plate and the first and second restraining plates. The first restraining plate and the first springs act together to resist movement in the xe2x80x9cXxe2x80x9d-direction and the second restraining plate and the second springs act together to resist movement in the xe2x80x9cYxe2x80x9d-direction.
In addition, there is provided, in accordance with a preferred embodiment of the present invention a rotatable mount for rotating a CCD sensor within a pre-determined degree of limitation from a first position to a second position. The rotatable mount supported by a CCD plate for retaining the CCD sensor, a shaft connected to the rotatable mount and adjustment means attached to the shaft for rotating the CCD plate within a pre-determined degree of limitation. The rotatable mount allows the plate to be moved through 90 degrees without the need to adjust the camera base.
Furthermore, in accordance with a preferred embodiment of the present invention, the rotatable mount is supported by means of a plurality of bearings within the CCD plate.
Furthermore, in accordance with a preferred embodiment of the present invention, the rotatable mount further includes a friction ring attached to the shaft for retaining the rotatable mount in position.
Furthermore, in accordance with a preferred embodiment of the present invention, the mount may be rotated either manually using a handle or by a motor.
In addition, there is also provided, in accordance with a preferred embodiment of the present invention, a method for sampling the light image from a CCD sensor in a digital camera, having a color filter array. The method includes the steps of:
sampling a first color component in a first position of the CCD sensor;
moving the CCD sensor along a first axis to a second position;
sampling the color component in the second position;
moving the CCD sensor along the first axis back to the first position;
moving the CCD sensor along a second axis to a third position, the second axis being perpendicular to the first axis;
sampling the color component in the third position; and
moving the CCD sensor along the second axis, back to the first position.
Furthermore, in accordance with a preferred embodiment of the present invention, the color filter array includes equal resolution for all color channels. Alternatively, the color filter array includes one higher resolution color channel. The higher resolution color channel may be green.